1. Field of the Invention
The present invention relates to a high-precision laser beam straight line scanner and its fabricating method. The scanner can perform the shaping of a beam generated by a diode laser, suppress the influence of a the jitter of a scanning beam due to the mode hopping of the semiconductor laser, and reduce the aberration of scanning beam.
Further, the present invention relates to a laser beam scanner having an aberration correcting holographic lens for generating an optimum incident wave, and to a method for fabricating the holographic lens.
Further, the present invention relates to a method for fabricating a hologram, in which a required astigmatism can be obtained in considering a difference between a reconstruction wavelength and a construction wavelength.
Further, the present invention relates to a method for fabricating a hologram which is used for a hybrid holographic lens. The hybrid holographic lens has a constitution to bring an optical spherical lens close to a flat plate hologram, or to fabricate a hologram on the optical spherical lens as well as having a feature that a wide image circle is realized. The present invention relates particularly to a method for fabricating a hologram in which an object wave is made incident easily.
Further, the present invention relates to a laser beam scanner which can suppress the deterioration of a scanning beam diameter due to the influence of variation of an oscillation wavelength of a semiconductor laser depending on its production lot.
2. Description of the Related Art
In the precision straight line scanning of a laser beam for a laser printer, attention is given to a laser beam scanner adopting a holographic scanner which is compact, light-weight, inexpensive, simple in structure, and easy to form, instead of a polygon mirror adopting a rotary polygon mirror, which is complex and expensive.
Prior art laser beam scanners are disclosed in Japanese Patent Publication (Kokai) Nos. 57-2018, 58-172617, 56-70517, 57-181523, etc.
However, these prior art laser beam scanners have problems such as an aberration of a scanning beam due to a difference in wavelengths to be used for constructing a hologram and for reconstructing the hologram, and the generation of an aberration due to the variation of wavelengths and the mode hopping of a laser beam so that the highly reliable laser beam scanning will not be realized.